Reconstruction of local and global marine paleoredox conditions for the northeast-Panthalassan (British Columbia, Canada) expression of the Toarcian Oceanic Anoxic Event using a multi-proxy approach

The Toarcian Oceanic Anoxic Event (T-OAE) of the Early Jurassic is one of several Mesozoic instances of expanded ocean anoxia, coupled with feedbacks and perturbations in Earth’s systems. The drivers for these feedbacks are debated, but the general consensus is that the event is initially rooted in the emplacement of the Karoo–Ferrar large igneous province. The T-OAE is also linked to a second-order mass extinction in the marine and terrestrial realms. Study of the T-OAE aims to provide insight into the causes and consequences of the environmental changes, which may be applicable at present given that some of the characteristics of the T-OAE (e.g. carbon inputs leading to global warming) are reflected in the modern environment. The purpose of this study, which focused on an Early Jurassic section containing the T-OAE in northeastern British Columbia, was to provide extensive insight into the local depositional environment, as well as a glimpse at the global ocean paleoredox conditions across the duration of the event. In northeastern British Columbia, the Early Jurassic is divided into the Gordondale Member and Poker Chip Shale of the lower Fernie Formation. The studied drill core contains both members; the Gordondale is the basal member composed of organic-rich, calcareous mudstone, whereas the overlying Poker Chip shale is a siliceous mudstone to siltstone unit. To provide context for the T-OAE in the study core, organic carbon isotope compositions were profiled in search of a telltale negative carbon isotope excursion (N-CIE) which signals the event zenith. The event was identified by an N-CIE in the uppermost 7 meters of the Gordondale Member below the contact with the Poker Chip Shale. Local paleoenvironmental reconstruction was accomplished using elemental redox sensitive trace metal geochemistry to determine the redox regimes (oxic, suboxic, anoxic or euxinic) and hydrography (open versus restricted) of the depositional basin. The Gordondale Member was characterised as anoxic to euxinic. Elevated Mo and V (up to 370 µg/g and 2757 µg/g, respectively) suggested some intervals were deposited in an euxinic environment. The U and Re concentrations are also elevated in the euxinic intervals (up to 36 µg/g and 878 ng/g, respectively). Intervals with lower Mo and V concentrations (< 53 µg/g and < 289 µg/g, respectively) but elevated U and Re content (up to 33 µg/g and 287 ng/g, respectively) indicated anoxic (non-sulfidic) conditions. The Poker Chip Shale was characterised by suboxic conditions (moderate Mo, V, U, and Re concentrations; < 21 µg/g, < 248 µg/g, < 6.3 µg/g, 86 ng/g, respectively). The cored interval was characterised as having been deposited in an open marine upwelling zone environment. This interpretation is based on an Mo–U covariation trend similar to the modern North and South American Pacific coastal basins (e.g. California, Mexico, Peru), and a Cd–Mo covariation trend indicating substantial primary productivity as a result of upwelling nutrient-rich deep waters. The T-OAE was a period where seafloor anoxia and/or euxinia is thought to have expanded across the global oceans. An estimate of the global area of seafloor anoxia and euxinia can be obtained from recently-developed mass balance models for elemental Re and Mo. Samples deemed anoxic (enrichment factors of U > 3.6 and Re > 100) or euxinic (anoxic, and enrichment factor of V > 3, S/Fe > 1.15) were grouped stratigraphically by those which occurred before the N-CIE (“Pre-N-CIE”), and during the N-CIE (two groups, “lower N-CIE” and “upper N-CIE”). The results of the mass balance model illustrated an expansion of anoxic and euxinic seafloor areas at the onset of the N-CIE (Pre-N-CIE to lower N-CIE) from ~1% to 6% of the total seafloor area. This was followed by a contraction of the anoxic and euxinic seafloor areas from ~6% to 4% of the total seafloor area from the lower to upper portion of the N-CIE. An attempt to link the expansion of anoxic and euxinic seafloor areas to Karoo–Ferrar large igneous province activity was made using a sedimentary Hg proxy. Previous study indicated that the utility of the proxy may decrease with increasingly distal (deeper waters, farther offshore) marine deposition. No distinctive Hg signature was associated with the N-CIE in the study core. As the study core was interpreted as having been deposited in a deep water/offshore environment, the lack of a Hg signal for volcanic activity was possibly affected by distal deposition. Thus, no conclusions were drawn from sedimentary evidence of enhanced volcanic activity. While no direct link to the Karoo–Ferrar province was made within the core, the mass balance models suggest that the T-OAE was indeed a period of expanded anoxic/euxinic seafloor area, at least in part. The maximum 6% total seafloor area covered by anoxia/euxinia was most likely located along the continental margins, thus the deep waters of the abyssal plains and central ocean likely remained oxygenated. These findings have demonstrated that the T-OAE was a minor event relative to the well-known “Big 5” mass extinctions, yet it was still associated with biodiversity loss. By monitoring modern anoxic/euxinic seafloor area, it may become possible to track the changes in Earth’s systems through comparison with these ancient OAE events

Global ocean redox changes before and during the Toarcian Oceanic Anoxic Event

This article is published by Springer Nature and is available here: https://doi.org/10.1038/s41467-023-36516-x This article is published Open Access and made available through a Creative Commons Attribution 4.0 International license: https://creativecommons.org/licenses/by/4.0/Mesozoic oceanic anoxic events are recognized as widespread deposits of marine organic-rich mudrocks temporally associated with mass extinctions and large igneous province emplacement. The Toarcian Oceanic Anoxic Event is one example during which expanded ocean anoxia is hypothesized in response to environmental perturbations associated with emplacement of the Karoo–Ferrar igneous province. However, the global extent of total seafloor anoxia and the relative extent of euxinic (anoxic and sulfide-rich) and noneuxinic anoxic conditions during the Toarcian Oceanic Anoxic Event are poorly constrained. Here we present estimates of the global total anoxic and euxinic seafloor areas before and during the Toarcian Oceanic Anoxic Event based on rhenium and molybdenum enrichments, respectively, in organic-rich mudrocks of the Fernie Formation (British Columbia, Canada). We find that mass balance models depict an expansion of up to ~7% total seafloor anoxia, which was dominated by euxinia, at the onset of the Toarcian Oceanic Anoxic Event, followed by a contraction before the end of the event. The global ocean redox trends revealed by the rhenium data mirrors the collapse and recovery patterns of global ammonite and foraminiferal biodiversity

Molybdenum isotope constraints on the origin of vanadium hyper-enrichments in Ediacaran-Phanerozoic marine mudrocks

Vanadium is an important redox-sensitive trace metal for paleoenvironmental reconstructions. Modern organic-rich sediments persistently contain sediment V enrichments 500 μg/g. Previous studies propose that ancient V enrichments of these magnitudes (“V hyper-enrichments”) were deposited from hyper-sulfidic bottom-waters with higher H2S levels (≥10 mM) than observed in modern euxinic basins. To test the importance of hyper-sulfidic conditions for generating V hyper-enrichments, we compare V concentrations with Mo isotope (δ98Mo) compositions from mudrock samples ranging in age from Ediacaran to Pleistocene. In the modern ocean, sediments deposited from strongly euxinic bottom waters ([H2S]aq > 11 μM) closely record global seawater δ98Mo because conversion of molybdate to tri- and tetra-thiomolybdate is quantitative. By contrast, large Mo isotope fractionations occur during Mo adsorption to Fe-Mn particulates or because of incomplete formation of the most sulfidic thiomolybdates in weakly euxinic settings ([H2S]aq < 11 μM), which both favor removal of lighter-mass Mo isotopes to sediments. We find multiple examples when mudrocks with V hyper-enrichments are associated with a wide range of δ98Mo for a single time interval, including values at or below oceanic input δ98Mo (0.3–0.7‰). This observation suggests significant isotopic offset from reasonable seawater values (typically ≥1.0‰). Thus, we conclude that hyper-sulfidic conditions were not responsible for many V hyper-enrichments in Ediacaran–Phanerozoic mudrocks. Instead, sediment V hyper-enrichments can be explained by high Fe-Mn particulate fluxes to weakly euxinic sediments or by moderately restricted euxinic settings with strongly euxinic ([H2S]aq > 11 μM but not necessarily > 10 mM) or weakly euxinic (with slow clastic sedimentation rates and high organic carbon fluxes) bottom waters where vigorous water exchange provides a continuous V supply from the open ocean

Species-Specific and Distance-Dependent Dispersive Behaviour of Forisomes in Different Legume Species

Forisomes are giant fusiform protein complexes composed of sieve element occlusion (SEO) protein monomers, exclusively found in sieve elements (SEs) of legumes. Forisomes block the phloem mass flow by a Ca2+-induced conformational change (swelling and rounding). We studied the forisome reactivity in four different legume species—Medicago sativa, Pisum sativum, Trifolium pratense and Vicia faba. Depending on the species, we found direct relationships between SE diameter, forisome surface area and distance from the leaf tip, all indicative of a developmentally tuned regulation of SE diameter and forisome size. Heat-induced forisome dispersion occurred later with increasing distance from the stimulus site. T. pratense and V. faba dispersion occurred faster for forisomes with a smaller surface area. Near the stimulus site, electro potential waves (EPWs)—overlapping action (APs), and variation potentials (VPs)—were linked with high full-dispersion rates of forisomes. Distance-associated reduction of forisome reactivity was assigned to the disintegration of EPWs into APs, VPs and system potentials (SPs). Overall, APs and SPs alone were unable to induce forisome dispersion and only VPs above a critical threshold were capable of inducing forisome reactions

MPER-specific antibodies induce gp120 shedding and irreversibly neutralize HIV-1

Antibody-mediated gp120 shedding and HIV neutralization exhibit similar kinetics and thermodynamic requirements

ConectCat : aplicación web : fiestas locales y otros servicios y puntos de interés en Cataluña

Aplicación web basada en mapas interactivos y timeline. Permite visualizar las fiestas locales así como otros servicios y puntos de interés de Cataluña

Contribution of intrinsic properties of neurons on network oscillations in the rat hippocampus

Der Hippokampus ist der wichtigste Umschalt- und Verarbeitungsort sämtlicher Informationen aus der Umwelt. Alle Signale werden über ihn zum Kortex und wieder zurück geleitet, wobei er sich kohärenter Netzwerkoszillationen bedient. Diese verschlüsseln zeitlich Informationselemente in neuronalen Zellensembles und heften sämtliche kognitive Erfahrungen zusammen, die wir schließlich als Wahrnehmung erleben bzw. zu denen wir über unser Gedächtnis Zugang erhalten. Besonders Gamma- und Theta-Oszillationen greifen dabei ineinander und ergänzen sich gegenseitig, so dass sie unverzichtbar für die Verarbeitung, Speicherung und Abrufung von Informationen sind. Sie unterliegen der synaptischen GABAergen und glutamatergen Übertragung, aber auch nicht- synaptischen Mechanismen und können experimentell in vitro pharmakologisch und stimulatorisch induziert werden. In vivo sind Netzwerkoszillationen jedoch nicht nur für oben beschriebene physiologische Aktivitätsmuster verantwortlich, sondern auch für Krankheitsbildern wie etwa Epilepsie. Oszillationen beschränken sich jedoch nicht nur auf Netzwerke, sondern sind auch in Form von Resonanz oder Membranpotentialoszillationen einzelnen Zellen zueigen. Zur Ausbildung dieser benötigen die Zellen intrinsische Eigenschaften zu denen Ionenkanäle wie der M-Strom (IM), h-Strom (Ih) und der persistierenden Na+-Strom (INaP gehören. Diese Ströme regulieren die Erregbarkeit von Zellen und können bei eingeschränkter bzw. überschießender Funktion ursächlich an Krankheitsbildern beteiligt sein. Aus diesem Grund beobachteten wir in extrazellulären Versuchen an hippokampalen Hirnschnitten die Auswirkungen verschiedener Ionenkanalmodulatoren auf Kainat-induzierte γ-und θ- Oszillationen sowie auf Stimulus-induzierte γ-Oszillationen. Wir applizierten den IM –Blocker XE991, die IM –Aktivatoren Icagen-110381 und Retigabine, den INaP -Blocker Losigamone sowie den Ih-Blocker ZD7288. Außer ZD7288 supprimierten alle Substanzen sowohl γ-als auch θ-Oszillationen, unabhängig von ihrem Induktionsweg. Abgesehen von synaptischen Interaktionen scheinen also auch intrinsische Eigenschaften von Neuronen bei der Aufrechterhaltung von γ- und θ-Oszillationen im Hippokampus von Bedeutung zu sein. Diese künstliche Supprimierung der Netzwerkoszillationen durch Modulation der Ionenkanäle steht stellvertretend für sämtliche Pathologien. Beide beruhen auf einer Membraninstabilität, die beim Menschen mit eingeschränkten kognitiven Fähigkeiten einhergehen. Somit kann man davon ausgehen, dass die Beschäftigung mit der Identifikation weiterer Ionenkanäle, bei der Suche nach neuen Medikamenten weiterhin eine große Rolle spielen wird.The hippocampus plays a crucial role in processing information from our environment. For communication with the cortex, it uses network oscillations, which encode for temporal elements of information and attach cognitive experiences, which we percieve and can even recall later from our memory. Especially gamma and theta oscillations go together and complement each other in this context. That is what makes them essential for processing, saving and recalling information. They not only depend on GABA-ergic and Glutamat-ergic mechanisms, but also on non-synaptic mechanisms and can be induced in vitro pharmacologically and by stimulation. In vivo, they occure not only physiologically, but also pathologically such as in epilepsy. Moreover oscillations can be looked at as intrinsic cell properties and messuerd as resonance and membrane potential oscillations. For shaping resonance or membrane potential oscillations those cells need ion-currents such as the M-current, h-current, or the persistent sodium current which regulate excitability of cells and can lead in case of dysfunction to pathology. In this work extracellular field potential recordings were used in adult rat hippocampal slices to verify the hypothesis that also intrinsic properties of hippocampal neurons contribute to network oscillations. Kainate application (100 nM) induced network theta frequency oscillations in coronal slices as well as network gamma frequency oscillations in horizontal slices. We tested for effects of the IM blocker XE991, the IM enhancer Retigabine and Icagen-110381, the INaP blocker Losigamone and the Ih inhibitor ZD7288. Except ZD7288 all substances suppressed both γ-and θ-Oszillationen which leads us to the assumption that besides synaptic interactions also intrinsic properties of neurones are important for sustaining oscillations in the hippocampus. Transferred from this in vitro setting to the pathologies in humans it might be possible that cognitive impairment in humans also results from instabilities in mambrane potentials. For this reason it seems meaningful to take a closer look at the identification of further ion-channels that might be involved in the genaration of membrane potential oscillations in order to develop efficiant drugs

Zulässigkeit einer geltungserhaltenden Reduktion der kartellrechtlichen Nichtigkeitsfolge

Ist ein Wettbewerbsverbot mit einer Laufzeit von 10 Jahren wegen Verstoßes gegen das Kartellverbot insgesamt nichtig oder bleibt es jedenfalls für eine Dauer von zulässigen zwei Jahren wirksam? Wie fällt die Bewertung bei geografisch oder sachlich überschießenden Abreden aus? Und gelten die Grundsätze nur für Wettbewerbsverbote oder für überschießende und daher kartellverbotswidrige Abreden insgesamt? Der Frage der Vereinbarkeit einer geltungserhaltenden Reduktion mit der kartellrechtlichen Nichtigkeitsfolge nähert sich die Autorin aus verschiedenen Perspektiven, die sowohl die Gemengelage zwischen europäischem Kartellverbot, nationalem Kartellverbot und allgemeinem Zivilrecht abbilden, als auch schadensersatz- und bußgeldrechtliche Konsequenzen der Methodik im kartellrechtlichen Kontext mit einbeziehen. Zur Untersuchung dieser Fragen greift die Autorin auf klassische juristische Auslegungsmethoden zurück und verfolgt darüber hinaus rechtsvergleichende und rechtsökonomische Überlegungen.»Admissibility of a Reduction of the Consequence of Nullity under Antitrust law that Preserves the Validity of the Agreement«: The author approaches the question of the compatibility of a validity-preserving reduction with the consequence of nullity under antitrust law from various perspectives, which both reflect the interplay between European and national antitrust prohibition and include general civil law, damages and fine law considerations. In doing so, the author draws on classical legal methods of interpretation, comparative law, and legal economic considerations

Wer kopiert verliert – über Verbreitung und Ursachen von Plagiaten

Sattler S. Wer kopiert verliert – über Verbreitung und Ursachen von Plagiaten. In: Bringezu U, Kunert A, eds. Der kleine Plagiats- und Täuschungskompass. Gießen: Technische Hochschule Mittelhessen; 2013: 6-8

Pea Aphid (<i>Acyrthosiphon pisum</i>) Host Races Reduce Heat-Induced Forisome Dispersion in <i>Vicia faba</i> and <i>Trifolium pratense</i>

Although phloem-feeding insects such as aphids can cause significant damage to plants, relatively little is known about early plant defenses against these insects. As a first line of defense, legumes can stop the phloem mass flow through a conformational change in phloem proteins known as forisomes in response to Ca2+ influx. However, specialized phloem-feeding insects might be able to suppress the conformational change of forisomes and thereby prevent sieve element occlusion. To investigate this possibility, we triggered forisome dispersion through application of a local heat stimulus to the leaf tips of pea (Pisum sativum), clover (Trifolium pratense) and broad bean (Vicia faba) plants infested with different pea aphid (Acyrthosiphon pisum) host races and monitored forisome responses. Pea aphids were able to suppress forisome dispersion, but this depended on the infesting aphid host race, the plant species, and the age of the plant. Differences in the ability of aphids to suppress forisome dispersion may be explained by differences in the composition and quantity of the aphid saliva injected into the plant. Various mechanisms of how pea aphids might suppress forisome dispersion are discussed